The present invention relates to methods for reducing the amount of contaminants in water, such as methods that utilize a chitosan salt disposed within a porous device that is at least partially immersed in running, contaminated, water.
Storm water which runs off land cleared of vegetation, such as on construction sites and other developed sites, typically exhibits a high degree of contamination due to the presence of suspended sediment, metals, oil and other chemicals and particulate matter. Stringent water quality standards, enforced under the Clean Water Act, have created the need to purify contaminated stormwater. In addition, many cities and states have environmental regulations that require developers to utilize Best Management Practices to meet water quality standards. These regulations mandate that contaminated water must be collected and treated to reduce contamination before discharging into the environment, such as into streams and vegetated areas.
There is therefore a continuing need for devices and methods to reduce the amount of contaminants in water before it is discharged into the environment. Preferably the devices and methods utilize materials that are not toxic to the environment.
In accordance with the foregoing, in one aspect the present invention provides purification devices for reducing the amount of contaminants in water, each device includes a water-soluble flocculant disposed within a body defining a multiplicity of pores, wherein the pores have an average diameter in the range of from 1 xcexcm to 2000 xcexcm. In operation, the purification devices of the present invention are at least partially submerged in running, contaminated, water which dissolves at least a portion of the flocculant. The dissolved flocculant forms water-insoluble complexes with one or more contaminants in the water. The complexes can be removed from the treated water, such. as by filtration. The purification devices of the present invention are therefore useful in any situation where reduction in the amount of contamination of water is desirable, such as in the treatment of turbid storm run-off water to reduce turbidity.
The present invention also provides methods for reducing the amount of contaminants in water. The methods of the invention each include the steps of: (a) at least partially immersing a purification device in running water, wherein (1) the purification device includes a water-soluble flocculant disposed within a body defining a multiplicity of pores, wherein the pores have an average diameter in the range of from 1 xcexcm to 2000 xcexcm; (2) the water comprises a contaminant; (3) the purification device is at least partially immersed in the running water under conditions whereby at least a portion of the flocculant is dissolved in the water and binds to at least some of the contaminant to form water-insoluble complexes; and (b) removing at least some of the water-insoluble complexes from the water. By way of example, at least some of the water-insoluble complexes can be removed from the treated water by dispersing treated water over a vegetated area; or dispersing treated water over a sand filter; or dispensing treated water into a settling tank wherein the water-insoluble complexes sediment.
The methods of the invention are useful in any situation where it is desired to reduce the amount of contaminants in water, such as, for example, reducing the amount of contaminants in water running off excavation and construction sites, and reducing the amount of contaminants in storm run-off water. The devices of the invention are useful, for example, in the methods of the invention.